1. Field
The present invention relates generally to magnetic read/write heads and methods of manufacture, and more particularly to methods of controlling the stripe height of magnetoresistive devices in magnetic read/write heads.
2. Description of the Related Art
Magnetic storage tape continues to be an efficient and effective medium for data storage in computer systems. Increased data storage capacity and retrieval performance is desired of all commercially viable mass storage devices and media. In the case of linear tape recording, a popular trend is toward multi-head, multi-channel fixed head structures with narrowed recording gaps and data track widths so that many linear data tracks may be achieved on a tape medium of a predetermined width, such as one-half inch width tape. To increase the storage density of magnetic tapes and storage systems, transducer elements, e.g., magnetoresistive (MR) elements or devices, on the head and data tracks on the tape are arranged with greater density.
Magnetic tape heads typically include an active device region including raised strips or ridges, commonly referred to as islands, bumps, or rails, that provide a raised tape support or wear surface across which the magnetic tape advances. One or more of these raised islands includes embedded data transducers. The embedded transducers can be either a recording device for writing information to a magnetic tape or a reproducing device for reading information from a magnetic tape. An embedded recording device produces a magnetic field in the vicinity of a small gap in the core of the device, which causes information to be stored on a magnetic tape as the tape advances across the support surface. In contrast, a reproducing device detects a magnetic field from the surface of a magnetic tape as the tape advances over the support surface. Additionally, raised islands may be included without transducers to help support and guide the magnetic tape over the head, generally referred to as outriggers.
Typically, a plurality of embedded transducers are spaced transversely across a direction of tape transport. The transducers may be sized and disposed along an island for varying storage tape data formats, e.g., different numbers of channels, track widths, and track densities. For example, a four channel head includes four read and four write transducers spaced transversely across a tape path. The width of the read/write transducers and the distance between adjacent read/write transducers is associated with the density of tracks to be written to and read from the storage tape. Storage capacity of magnetic tapes are generally increased with the use of smaller more closely positioned read/write transducers in the tape head.
As the storage tape and tape drive industry evolves and achieves increases in storage capacity, the tape head and media designs continue to make changes from one generation to the next. For instance, new data formats with more densely positioned read/write transducer elements on tape heads, more densely positioned tracks on the storage tape, and thinner storage tape increases the storage capacity of storage tape devices. For example, to increase storage capacity of storage tape, the storage tape may be thinned, e.g., lower magnetization thickness (Mrt), while narrowing and thinning the MR devices in the head.
Typical MR devices for use with magnetic recording heads are manufactured using standard semiconductor type processing methods. For example, multiple rows of magnetic recording transducers are deposited simultaneously on wafer substrates and cut into active device regions for incorporation into a magnetic recording head. After a section of magnetic recording transducers are cut from the wafer, they are subject to a lapping process to reduce the stripe heights of the MR devices to a desired height and smooth or polish the surface of the structure. Stripe height is one of the key parameters that control the signal output and device behavior of a magnetoresistive recording head. The stripe height generally determines the sensitivity of the magnetoresistive device to a magnetic field, where a reduction in stripe height typically produces a more sensitive magnetoresistive device. As magnetic recording density increases, scaled down MR devices, e.g., anisotropic magnetoresistive (AMR) or giant magnetoresistive (GMR) devices, are used to achieve adequate signal output. As MR devices scale down, stripe height scales down accordingly.
The desire for shorter stripe height leads to a desire for tighter control of stripe height during manufacturing, which is generally accomplished by mechanical lapping using one or more Electronic Lapping Guides (ELGs). It is generally unwise to use the actual MR devices for monitoring stripe height because of the potential for electrostatic discharge during the lapping process, which may damage the device. In the manufacture of typical multi-channel tape heads on a wafer, for example, a pair of ELGs is disposed at each end of a cluster of MR devices. The ELGs are monitored during manufacturing to determine the stripe height of the active MR devices of the cluster. For example, the lapping process is controlled to cease when the ELG resistance reaches a calculated value associated with a desired stripe height of the MR devices. The calculated ELG resistance, however, is subjected to variations in the geometry and material thickness of the ELG devices, which may result in large cluster-to-cluster stripe height variations.
It is desired to provide tighter control over stripe height during manufacturing, e.g., to provide smaller stripe heights and more densely configured magnetoresistive devices for recording heads.